Method for fabricating a flexible and reinforced tubing

ABSTRACT

Disclosed here within is the method of manufacture of a reinforced and flexible tube or catheter that can be used in a variety of applications. The first method of embedding the metallic coil or braided wire comprises the steps of engaging the metallic structure over the outer surface of the tubular member, applying heat through an appropriately sized mold to the outer surface of the tubular member while creating a pressure differential between the inner lumen and the outside surface of the tubular member for a specified period of time. The second method of embedding the metallic coil or braided wire comprises the steps of engaging the metallic structure onto the outer surface of a mandrel, positioning the mandrel/metallic structure within the lumen of the tubular member, placing the tubular member within an appropriately sized mold, applying heat through the mold to the tubular member while creating a pressure differential between the inner lumen and the outside surface of the tubular member for a specified period of time.

PRIOR APPLICATIONS

This application is a divisional of application Ser. No. 08/734,682filed on Oct. 21, 1996, now U.S. Pat. No. 5,879,342.

FIELD OF THE INVENTION

The present invention relates to a composite tubing for use in a varietyof applications and a method for manufacturing the invention. Thepresent invention pertains to a flexible and reinforced tubing which cantransmit rotational (i.e. torque) and translational (i.e. push-pull)motion. In additional, the present invention pertains to a method formanufacturing the reinforced and flexible invention. The presentinvention is particularly, through not exclusively, useful as areinforced and flexible tube for use in medical applications such as aguiding catheter or a catheter with preferred torque, flexibility andpushable characteristics.

BACKGROUND OF THE INVENTION

A large number of reinforced tubing devices have been introduced for usein a wide variety of applications. For example, flexible reinforcedtubing is commonly used to transmit translational motion (i.e.,push-pull) or rotational motion (i.e., torque) from a control apparatusto an object located distally which is to be manipulated or moved. Anexample of one such device is the reinforced tubing disclosed in U.S.Pat. No. 5,101,682, which can be used in medical applications andincludes a surrounding layer of electroplated material covering andbonded to the tube. Another example of a reinforced tubing device isdisclosed in U.S. Pat. No. 3,769,813 for a resilient torque tube that isreinforced with alternate layers of wire net and rubber and is useful invehicle transmissions.

Another important consideration in the design of reinforced tubingdevices is the need for adequate tubing resilience (i.e., resistance topermanent deformation, kinking, and buckling under stress). Also, it maybe desirable that the reinforced tubing be highly flexible for certainapplications, such as for providing a conduit for fluid flow. It mayalso be desirable that the tubing retain sufficient strength to functioneffectively as a torque transmitter.

In one application, such as intravascular catheters used to advancemedical devices to the arterial system surrounding the heart, there is aneed for the catheter to be flexible but nevertheless, also exhibit acertain amount of stiffness so that the catheter may be advanced throughvarious twists and turns presented by the arterial system. Also, whilethe body of the catheter must exhibit the desired characteristics offlexibility and stiffness, the catheter lumen must have a low frictionsurface so that an inner catheter or guidewire can be easily advancedthrough the lumen. An example of one such device which can be used inmedical applications and discloses an invention which exhibits thecharacteristics of flexibility and stiffness is U.S. Pat. No. 5,538,510which employs coextruded tubular members to achieve the desired results.The disadvantage of this coextrusion invention is that the manufacturingprocess of this device is complex and has the potential for relativelythick walls and large profiles.

While each of the reinforced tubing devices discussed above can fulfillat least one of the above requirements, there is still a need for asingle reinforced tubing device which can be used interchangeably in avariety of applications and which will simultaneously provide all orseveral of the characteristics mentioned above. To satisfy this need,the present invention recognizes that a reinforced tubing device can beprovided which is relatively strong, flexible and thin walled, and whichdoes not easily kink, permanently deform, or buckle under stress.

Accordingly, it is an object of the present invention to provide a thinwalled reinforced tubing device which is both relatively flexible andstrong.

It is a further object of the present invention to provide a reinforcedtubing device that efficiently transmits translational and rotationalmotion without easily buckling, kinking, or permanently deforming.

Yet another object of the present invention is to provide a reinforcedtubing device that yields a specific inner lumen configuration whichreduces the overall internal contact area and thereby reduces thefrictional drag imparted to objects passing through it.

Another object of the present invention is to provide a method ofreinforcing a tubular member which can vary certain properties, such asflexibility, along the length of the tubing.

Another object of the present invention is to provide a method offabricating flexible tubing from materials not known to have flexiblecharacteristics or from materials with a relatively high modulus.

Another object of the present invention is to provide a tubularstructure containing a multitude of protruding elements which, inresponse to bending or flexing stresses, modify their configurationrather than and thereby minimize significant elongation and compressionof the base material.

Yet another object of the present invention is to provide a reinforcedtubing with relatively a thin wall and maintaining the characteristicsdescribed in the above six paragraphs.

Another object of the present invention is to provide a reinforcedtubing device which can be used in a wide variety of applications.

Yet another object of the present invention is to provide a reinforcedtubing device that is easy to use and relatively cost effective tomanufacture.

SUMMARY

For the foregoing reasons, there is a need for a flexible, reinforcedand relatively thin walled tubular member that incorporates the featuresdescribed herewith and that can be inexpensively manufactured.

The present invention is directed to a tubular member that has acontinuous annular wall that defines an inner lumen and at least onehelical structural member that is embedded within the outer or innersurface of the tube wall. The helical coil or braided structure can beembedded to various depths; within the outer surface or inner surface ofthe tubular member. It is also an object of the present invention tovary the embedding depth or pitch characteristics of the helical memberalong any portion of a tubular member to modify the flexibility andtorque characteristics over the longitudinal length of the tube.Therefore, the present invention yields a number of ridges or othershaped protrusions projecting into the lumen. These protrusions functionto reduce the internal contact area and therefore reduce frictional dragwhen another structure is being passed through the internal lumen.

One method of manufacturing the present invention includes the steps ofengaging a helical member, e.g., a braid or coil, onto the outer surfaceof the tubular member to form a processing composite tubular memberhaving a first end, a second end, and at least one inner lumen. Thetubular member can be either a single or multi-luminal configuration.The processing tubular member is positioned in an appropriately sizedheating mold, a system to create a pressure differential is appliedbetween the outer surface of the processing tubular member and the innerlumen by engaging a pressure source to the inner lumen of said tubularmember, said processing composite tubular member is then heated to atemperature within a range for a first period of time, while eithersimultaneously or after a second period of time, a first pressure isapplied to said lumen of said composite tubular member for a thirdperiod of time, after which said first pressure is reduced to a secondpressure, and the composite tubular member is allowed to cool, resultingin a reinforced tubular structure.

Another method of manufacturing the present invention includes the stepsof engaging a helical member, e.g., a braid or coil, onto the outersurface of a mandrel and positioning this helical member/mandrelassembly within the inner lumen of the tubular member forming aprocessing composite assembly, said processing composite assembly isthen placed within an appropriately sized heating mold, a system tocreate a pressure differential is applied between the outer surface andthe inner lumen of the tubular member by engaging a vacuum source to theinner lumen of the tubular member and supplying a pressure source to theouter surface of the tubular member or, said processing compositeassembly is then heated to a temperature within a range for a firstperiod of time while either simultaneously or after a second period oftime, the pressure differential is created by applying a first pressureto the outer surface of the tubular member and a first vacuum to theinner lumen of the tubular member, said pressure differential is appliedfor a third period of time, after which the pressure differential isreduced to a null, and said composite tubular member allowed to cool,resulting in a processed composite tubular member.

During the fabrication process, the mold can be shaped such that theprocessed reinforced tubular member is final configured with one or moreradii. in addition, the mold can be configured such that the processedreinforced tubular member yields a substantially circular, oval,triangular# or other geometric shape in cross section.

After the reinforced tube is processed, either the outer surface, theinner surface, or both surfaces, can be coated with a suitable material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the novel reinforced tubing in oneintended environment, showing the tubing positioned in an artery and inoperative association with a balloon catheter device.

FIG. 2 is a perspective/sectional view showing the tubular member withthe helical member, e.g., a coil or braid, in contact with the outersurface of the tubular member and positioned within a thermal source,and the lumen of the tubular member engaged with a pressure source.

FIG. 3 is a sectional view showing the tubular member with the helicalmember in contact with the outer surface of the tubular member forming apre-processed composite tubular member, the lumen of the tubular memberengaged with a pressure source and the pre-processed composite tubularmember positioned within a thermal source;

FIG. 4 is a sectional view showing the processed reinforced tubing withthe helical member embedded in various depths within the tubular member.

FIG. 5 is a sectional view showing the reinforced tubing with thehelical member embedded in a fixed depth into the tubular member anddemonstrating the multiple convex ridges protruding into the lumen.

FIG. 6 is an magnified sectional view showing the relationship of thetubular member with the embedded helical member, e.g., a braid or coil;

FIG. 7 is a side elevational view showing the method of calculating thepitch angle of the helical member.

FIGS. 8a, 8 b, and 8 c are side elevational views showing the reinforcedtubing in a triangular (8 a), oval (8 b) and square (8 c) configuration.

FIG. 9 is a side elevation view of the multiple lumen design of thereinforced tubing.

FIG. 10 is a sectional view showing the tubular member with a helicalmember, e.g., a coil or braid, engaged to a mandrel and positionedwithin the lumen of the tubular member forming a processing structurewhich is positioned within a thermal source and connected to pressuredifferential sources.

FIG. 11 is a sectional view showing the reinforced tubing with the coilor braid embedded in a fixed depth into the tubular member anddemonstrating the multiple convex ridges protruding into the lumen andprojecting out from the outer surface.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Initially referring to FIG. 1, it can be seen that a reinforced tubing,generally designated 10, may be operatively associated with variousancillary devices in various diverse applications. For example, FIG. 1shows tubing 10 operatively associated with an angioplastyinflation/deflation apparatus 7 and an expandable angioplasty balloon14. In the application of tubing 10 shown in FIG. 1, tubing 10 is aguiding catheter for providing access from the femoral artery to thecoronary vasculature to balloon catheter 14. In this application, thetubing 10 must be flexible to minimize damage to the aorta and possesstransmitting torque capability to position the tip of the guidingcatheter to the orifice of a coronary artery. Tubing 10 is also aconduit for communicating fluid to the coronary artery once properlypositioned. While FIG. 1 illustrates one potential application of tubing10, it is to be understood that the application shown in FIG. 1 ismerely exemplary. As a further example of a potential application forthis invention, tubing 10 could be used as a connector between a fluidsource and a fluid receiver for fluid communication applicationsrequiring a strong, relatively thin walled yet flexible hose connector,or as a control cable and fluid conduit in a surgical atherectomyapparatus.

Turning now to FIGS. 2 and 3, the details of preprocessed reinforcedtubing 10 can be seen. There, tubing 10 is shown to include a hollowtubular member 30 in juxtaposition with the helical member (braid orcoil) 36 to form a pre-processed tubular composite. FIGS. 2 and 3 alsoshows a processing mold 17 which is in contact with thermal source(heater) 15 and which is in juxtaposition with the pre-process tubularcomposite. Also shown is a representation of a temperature controlsystem 20 and a variable pressure source 11.

As best shown in FIGS. 2 and 3, the pre-processed tubular member has acontinuous, substantially cylindrical annular wall 31 which defines aninner surface 32 and an outer surface 29. Wall 31 of tubular member 30also defines a central hollow lumen or passageway 28, through whichliquid or gas can flow in connection with, for example, angioplastysurgery applications of tubing 10. Importantly, the dimensions of tube30 (and tubing 10) may be established as appropriate for the particularapplication of tubing 10. It is to be understood, however, that theouter diameter, the inside diameter and the thickness of the wall 31 oftube 30 may be adjusted to meet the criteria of an appropriateapplication. Furthermore, the length of tubing 10 may be established asappropriate for the particular application of tubing 10. For example,tubing 10 may have a length which can vary between a few inches andseveral yards.

Additionally, tube 30 is preferably made of strong yet flexiblepolymeric materials, such as polyamide, polybutylone terephthalate,polyetherimide, polyethylene, polyethylene terephthalate, polyethylenenapthalate, or any combinations thereof. It is not essential that the,base polymeric material have flexible characteristics or have a lowmodulus. The process disclosed herein will tender a high modulus,inflexible base material to have characteristics which in the presentinvention, greatly exceeds the flexibility of a tubular member that ismerely extruded using such a base material. As the skilled artisan willappreciate, the material of tube 30 may also be selected to becompatible with the particular application of tubing 10. For example,certain applications of tubing 10 may dictate that the material of tube30 be chemically compatible with certain fluids which may becommunicated through passageway 28 of tube 30, and further that thematerial of tube 30 be nontoxic and nonoxidizin4.

Furthermore, tubular member can comprise a multiple lumen configuration(FIG. 9). The multiple lumen configuration will have the thin wall,flexible and reinforced characteristics similar to the single lumendesign yet have an assortment of lumens where each lumen can have adifferent and independent function.

Referring to FIGS. 2 and 3 demonstrating the pre-processed compositemember and FIG. 4 demonstrating the post-processing configuration, thehelical member 36 is shown in juxtaposition to outer surface 29 oftubular member 30. More particularly, as shown in FIG. 4, helical member36 is positioned on tubular member 30 to form a succession of spacedapart coils 43 whose respective edges do not contact each other. Also,although the present invention uses a wire for helical member 36, it isto be understood that the geometry of helical member 36 may be anygeometry suitable for providing structural support for tube wall 31,such as a flat ribbon or triangular configuration. Importantly, helicalmember 36, should be made of a material which, when helically isjuxtaposition to the outside surface of tubular member 30, providessufficient hoop strength to structurally strengthen tube wall 31. In thepresent invention helical member 36 is composed of tungsten or stainlesssteel, but it is to be understood that other materials may be used whichfulfill the strength and bonding requirements discussed above, such asmolybdenum, cobalt, nickel, or combinations thereof It is also withinthe scope of this invention that non-metallic materials may be employedas the helical member 36, such as nylon, carbon or boron fibers, oraromatic polyamide fibers (e.g. Kevlar®).

In addition to the material requirements of helical member 36 disclosedabove, it will be recognized by the skilled artisan that the dimensionsand configuration of member 36 will have a significant effect on theoperational capabilities of tubing 10. On the one hand, these variablesmust be selected to provide sufficient structural support for tube wall31. on the other hand, (for certain applications of tubing 10) thevariables must be selected to minimize the wall thickness of tubing 10.For example, when tubing 10 is to be used in the angioplasty surgeryapplication shown in FIG. 1, thickness of helical member 36 may rangefrom one half thousandth (0.0005″)of an inch to twelve thousandth(0.012″) of an inch, preferably ranging from one to four thousandths(0.001″-0.004″) of an inch in diameter. The is preferred range isdesirable in human clinical applications to minimize the profile oroverall outside diameter while maximizing the lumen diameter of thedevice to match dimensional limitations of the human vasculature. Forother applications which require even greater strength of tubing 10,helical member 36 may be relatively thicker.

As the skilled artisan will also readily appreciate, an angular pitch 41between the successive coils 43 of helical member 36, can be selected toprovide for flexibility as well as for sufficient torque transmissioncharacteristics in tubing 10. In fact, the present invention envisions apitch angle 41 (defined as the angle between a line perpendicular to thelongitudinal axis and the slope of one of the coil or braid stands)along the length of tubing 10 which can be varied between one (1) degreeand ninety (90) degrees, preferably between five (5) and forty five (45)degrees, 40 flexibility and torque transmission requirements dictate.For example, pitch angle 41 may be relatively high (about forty five(45) degrees) at one end of tubing 10 for maximum tor a transmission.Pitch 41 may then be gradually or suddenly decreased to about five (5)degrees at the second end of tubing 10 to provide for more flexibilityof tubing 10 near either end or varied along its length.

In one method of manufacturing the embodiment shown in FIGS. 4, 5 and 6,helical member 36 becomes embedded, from the outer surface 29, into tubewall 31. Initially, helical member 36, being a braid or coil, is engagedonto the outer surface 29 of the tubular member 30 to form apreprocessed composite tubular member having a first end, a second end,and an inner lumen. Then, the pre-process composite is positioned in anappropriately sized heating mold 17, whereby a pressure source isengaged to the inner lumen 28 of tubular member 30. Heat is applied tothe composite tubular member using a temperature range for a specifiedperiod of time. Typically the temperature range is dependent on thepolymeric material employed, and may range anywhere from 100 degreesFahrenheit to 880 degrees Fahrenheit depending on the polymericmaterial. When tubing 10 is being used as a guiding catheter and thepolybutylene terephthalate material is employed, the preferable range isfrom 350 degrees Fahrenheit to 420 degrees Fahrenheit. In an anotherembodiment, for example, when tubing 10 is being used as a torque tubein medical applications and the polyamide material is employed, thepreferable range is from 275 degrees Fahrenheit to 350 degreesFahrenheit. Since various polymeric materials could be utilized in thisprocess, the temperature range is dependent on, and therefore adjustedfor, the polymeric material employed.

Either simultaneously or after a predetermined time period has passed, afirst pressure is applied to the lumen 28 of the composite tubularmember 30 to cause the pressure differential across the tube wall.Typically the pressure range is dependent on the diameter and wallthickness of the tubular member employed, and therefore may rangeanywhere from 20 psi to 5000 psi depending on specific parameters of thetube. When tubing 10 is being used as a guiding catheter and thepolybutylene terephthalate material is employed, the preferable range isfrom 300 psi to 550 psi. in an another embodiment, for example, whentubing 10 is being used as a torque tube in medical applications and thepolyamide material is employed, the preferable range is from 450 psi to650 psi. Since a wide range of tubular diameter and wall thickness couldbe utilized in this process, the pressure range is dependent on theseparameters.

After the processing time has expired, the first pressure is reduced toa second pressure. Finally the composite is tubular member 30 allowed tocool resulting in a processed reinforced tubing 34.

It is to be appreciated that the processed structure disclosed aboveresults in the braid or coil member 36 becoming embedded into the wall31 of processed tubular member 34. As the skilled artisan will alsoreadily appreciate and as demonstrated on FIG. 4, the temperature,pressure or time can be adjusted during the process to result in varyingthe depth of which the coil or braid 36 becomes embedded in wall 31 ofprocessed tubular member 34. These process parameters may then begradually or suddenly reduced or increased along the length of thetubular member to result in various depths that the coil or braidbecomes embedded. Furthermore, as the braid or coil member 36 becomesembedded into the wall 31, one or more projecting elements protrude fromthe inner surface 32 of tubular structure 30. such elements 38, as showsin FIGS. 4 and 5, result in a ridge which conforms to and surrounds theembedded helical member. It is also possible that these elements can beformed in a specific configuration, such as a parallelogram, trapezoidor triangle.

Importantly, the dimensions of tubular member 30 (and tubing 10) may beestablished as appropriate for a number of applications which result inthe formation of particular tubular member. For example, when tubing 10is being used As a guiding catheter for angioplasty applications, innerdiameter of tube 30 may range from approximately thirty nine thousandth(0.039″) of an inch to four hundred and forty five thousandth (0.445″)of an inch, preferably from sixty thousandth (0.060″) of an inch to onehundred and twenty five thousandth (0.125″) of an inch, and the outsidediameter of tube 30 may range from fifty three thousandth (0.053″) of aninch to four hundred and fifty eight (0.458″) of an inch, preferablyfrom seventy nine thousandth (0.079″) of an inch to one hundred andforty four thousandth (0.144″) of an inch. The preferred inside andoutside diameters are appropriate for currently marketed angioplasty andinterventional devices that would be used with the guiding catheterapplication.

In another embodiment, for example, when tubing 10 is being used as atorque tube in medical applications, inner diameter of tube 30 may rangefrom approximately twelve thousandth (0.012″) of an inch to four hundredand forty five thousandth (0.445″) of an inch, preferably from fortythousandth (0.040″) of an inch to seventy thousandth (0.070″) of aninch, and the outside diameter of tube 30 may range from sixteenthousandth (0.016″) of an inch to four hundred and fifty eight (0.458″)of an inch, preferably from fifty two thousandth (0.052″) of an inch toninety thousandth (0.090″) of an inch. The preferred diameters areappropriate for 30 currently marketed angioplasty and interventionaldevices.

It is to be understood that the processed structure disclosed aboveresults in several advantages. First, tubing 10 is a flexible yet stronghollow and relatively thin walled tube which can effectively transmitboth translational motion and rotational motion (i.e., torque). Thus,tubing 10 can be used as A control cable or torque conveyor in a varietyof applications. Second, the structure disclosed above results in atubing 10 which will not readily kink or permanently deform when bent.Third, tubing 10 will not readily buckle under tensile or compressivestress, such as what may be generated when tubing 10 is being used totransmit translational and/or rotational motion. Fourth, the presentinvention does not require materials known to have flexiblecharacteristics or materials with a low modulus. Fifth, the presentinvention provides a tubular structure containing a multitude ofprotruding elements which, in response to bending or flexing stresses,modify their configuration and thereby minimize significant elongationand compression of the base material. Sixth, the present inventionprovides a reinforce tubing device that yields a specific inner lumenconfiguration which reduces the overall internal contact area andthereby reduces the frictional drag imparted to objects passing throughthe lumen.

Certain applications of tubing 10 may require that a coating (not shown)be applied to the outer surface 33 of the processed composite tubing 34.Suitable materials for such a coating can be polyetherimide,polyethylene, polyurethane, silicone products, parylene, or lubricoushydrophilic coatings.

In a second method of manufacturing the embodiment shown in FIGS. 10 and11, helical member 46 becomes embedded into tube wall 51 of tubularmember 50 through the inner surface 52. Tubular member 50 is defined byhaving a first end, a second end, and an inner lumen 48. Initially, ahelical member 46 e.g., braid is engaged onto the exterior surface ofmandrel 42 which is positioned and centered within lumen 48 of tubularmember 50. The pre-process composite is then positioned in anappropriately sized heating mold 18. A system for creating a pressuredifferential is applied between the outer surface 49 and the inner lumen48, by engaging a vacuum source 62 to the inner lumen 48 of tubularmember 50 and applying a pressure source to the outer surface 49 oftubular member 50. As shown in FIG. 10, heating mold 18 is connected toa variable pressure source 61 to create a pressure which engages theouter surface 49 of tubular member 50. A spacer 44 functions to seal thesecond end of heating mold 18. As a skilled artisan can appreciate,several methods of obtaining a pressure differential between the innerlumen 48 and outer surface 49 (across the wall) of the tubular member 50are available. Heat is applied from mold 18 to the composite tubularmember into a temperature range for a first period of time. Eithersimultaneously or after a second time period, the pressure differentialis created by applying a first pressure to the outer surface of thecomposite tubular member 50 and a first vacuum to the inner lumen of thecomposite tubular member 50. After the processing times have expired,the pressure differential is reduced to a null and the composite tubularmember 50 is allowed to cool. The mandrel is removed, resulting in aprocessed reinforced tubing 53.

It is to be understood that the processed structure disclosed aboveresults in the braid or coil member 46 embedded through the innersurface 52 and into the wall 51 of tubular member 50. As the skilledartisan will also readily appreciate, the temperature, vacuum, pressureor time can be adjusted during the process to result in varying thedepth of which coil or braid 46 becomes embedded in wall 51 of tubularmember 50. These process parameters may then be gradually or suddenlyreduced or increased along the length of the tubular member to result invarious depths that the coil or braid becomes embedded.

The details of the operation of tubing 10 will vary according to theparticular application of tubing 10. When tubing 10 is to be used as atorque transmitter/control cable, tubing 10 is operatively associatedwith the particular control apparatus being used, such as the apparatus7 shown in FIG. 1, or a motor throttle (not shown) or even a person'shand (not shown). Distal end of tubing 10, in contrast, can be attachedto the, mechanism being manipulated, such as the angioplasty balloon 14shown in FIG. 1. Translational motion and torque may then be transmittedthrough tubing 10 from the particular Control apparatus being used tothe mechanism being manipulated. At the same time, because tube 30 ishollow, fluid or gas may be communicated between the proximal end andthe distal of tubing 10.

While the particular reinforced tubing as herein shown and disclosed indetail is fully capable of obtaining the objects and providing theadvantages herein before stated, it is to be understood that it ismerely illustrative of the presently preferred embodiments of theinvention and that to limitations are intended to the details ofconstruction or design herein shown other than as described in theappended claims.

I claim:
 1. A method for reinforcing a tubular structure for medicaldevices which comprises the steps of: (a) engaging at least one helicalmember onto an outer surface of a tubular member to form a compositetubular assembly having a first, a second end, and an inner lumen; (b)positioning said composite tubular assembly in a heating mold; (c)heating said composite tubular assembly into a temperature range, saidtemperature range being between a first temperature and a secondtemperature; (d) creating a pressure differential between said outersurface and said inner lumen; (e) reducing said pressure differential;(f) removing said composite tubular assembly from said heating mold toresult in a reinforced tubular structure; and (g) applying a coating onan inner surface of said reinforced tubular structure.
 2. A method asrecited in claim 1 further comprising the steps of: applying a coatingon said outer surface of said reinforced tubular structure.
 3. A methodas recited in claim 1 wherein said heating mold is configured such thatsaid reinforced tubular structure results in having one or more radii.4. A method as recited in claim 1 wherein said reinforced tubularstructure is oval, triangular, or square in cross section.
 5. A methodfor reinforcing a tubular structure for medical devices which comprisesthe steps of: (a) engaging at least one helical member onto a mandrel toform a processing assembly; (b) positioning said processing assemblyinside a tubular member to form a composite tubular assembly, saidtubular member having an outer surface, an inner surface and an innerlumen; (c) positioning said composite tubular assembly in a heatingmold; (d) heating said composite tubular assembly into a temperaturerange, said temperature range being between a first temperature and asecond temperature; (e) creating a pressure differential between saidouter surface of said tubular member and said inner lumen of saidtubular member; (f) reducing said pressure differential; (g) removingsaid composite tubular assembly from said heating mold to result in areinforced tubular structure; and (h) applying a coating on an innersurface of said reinforced tubular structure.
 6. A method as recited inclaim 5 further comprising the steps of applying a coating on the outersurface of said reinforced tubular structure.
 7. A method as recited inclaim 5 wherein said reinforced tubular structure results in having oneor more radii.
 8. A method as recited in claim 5 wherein said reinforcedtubular structure results in having an oval, triangular, or square crosssection.